Dynamic Host Configuration Protocol (DHCP) message is used in Internet so that a server may allocate configuration information to a host in the network. The configuration information contains dynamically allocated network addresses and additional configuration options, wherein the configuration options include Domain Name Server (DNS) addresses, physical locations of Internet hosts, and so forth. The additional configuration options are encapsulated in DHCP options and are transmitted in plain text.
When a host (a DHCP client) is accessing the network, the host first initiates a request in search of a DHCP server in the network, requesting the DHCP server to allocate a network address, wherein the request may include requested additional configuration options. Upon receipt of the request from the DHCP client, the DHCP server in the network transmits a message including an allocated network address and the additional configuration information to the DHCP client, wherein the additional configuration information is encapsulated in the configuration options of the message for transmission. In the case that the DHCP client and the DHCP server are not located on a same network segment, there may be a DHCP relay agent between them. The DHCP client initiates a request to the DHCP relay agent, and the DHCP relay agent adds additional information upon receipt of the request from the DHCP client to assist the DHCP server to implement network address selection and parameters configuration. The additional information is encapsulated in relay agent options, and is stored in different relay agent options respectively. After adding the additional information into the request, the DHCP relay agent forwards the request to the DHCP server. The DHCP server responds to the DHCP relay agent a message carrying additional information, network address and attached configuration options. And then the DHCP relay agent sends the message carrying additional information, network address and attached configuration options to the DHCP client. There are some circumstances that the DHCP relay agent may send a DHCP request to the DHCP server, requesting to update information stored in the DHCP relay agent, wherein the request carries the relay agent options added by the DHCP relay agent. The DHCP server may respond to the DHCP relay agent a message carrying the relay agent options according to the request sent from the DHCP relay agent.
There is multitudinous configuration information in the additional configuration options transmitted by the DHCP server. Some user sensitive information, the physical location of a user, for instance, might be included therein, and each configuration option corresponds to one piece of user sensitive information. When the DHCP relay agent forwards the request, some user sensitive information such as authentication information may also be added and transmitted to the DHCP server. Since the user sensitive information is transmitted in plain text, it is at a high risk of being stolen during transmission. As a result, this fails to keep the user sensitive information in privacy.